## ProMC Files

ProMC [Che14] is a library for the storage of Monte Carlo event records, or other data, in a very compact binary form. It provides routines for fast input to and output from these compact data files. It uses "varints" as a way to store and compress an integer using a variable number of bytes, based on Google's platform- and language-neutral Protocol Buffers. Real numbers are converted to integers, e.g. by specifying a smallest unit of energy, momentum and length. Thereby a low-energy particle can be represented by a smaller number of bytes.

The current PYTHIA linking and interface is based on ProMC version 1.5; earlier version will not do. Once you have to installed the ProMC library, you should configure PYTHIA with

      ./configure --with-promc=/path/to/ProMC

and recompile the PYTHIA library. As usual more fine-grained options are available to set paths to binaries, libraries and headers separately, if need be.

The `examples/main46.cc` sample program illustrates how to write PYTHIA events onto a ProMC file.